The invention relates generally to mass storage systems, and in particular, to the communications for, and configuration of, a mass storage system.
To meet the growing requirements of today's computer systems, and simultaneously, to achieve flexibility and reliability in the function and configuration of a mass storage system, manufacturers of such systems have needed to make their systems adaptable to differing host standards. However, it would be desirable to manufacture the same mass storage system for use with the differing standards associated with various host computer manufacturers.
One particular area in which the standards have clearly not been consistent is the data block structure with which a host computer system formats its data. Thus, in a Unisys Series A system, for example, each block has 180 bytes of data whereas in an IBM AS/400 system, each block has 520 bytes of data. Other system configurations, such as those using the Unix operating system, require 512 bytes of data per block (the defacto standard). In addition, there can be one or more bytes of error correcting code or parity as required by the host system.
In modern high speed, high capacity systems, the host system does not perform the actual storage of the data on or in the mass storage device. This is left to a sophisticated storage controller which receives the blocks of data and formats them for storage in view of the physical characteristics of a disk drive.
Most disk drive manufacturers configure their disk drives for 512 bytes of data per block, with a plurality of blocks forming a track. (Those made for compatibility with IBM equipment such as the AS/400, use 520 bytes per block.) Each drive contains a plurality of tracks to form a cylinder. It is necessary in accordance with prior art systems to configure the physical disk drive, at the factory, for differing protocols, and thus create drives which cannot be used for any other block size protocol without being returned to the factory.